S-C Hung1, C-C Wu2, C-J Lin2, W-Y Guo3, C-B Luo2, F-C Chang2, C-Y Chang2. 1. From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanDepartment of Biomedical Imaging and Radiological Sciences (S.-C.H.)School of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan. 2. From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanSchool of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan. 3. From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanSchool of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan. wyguo@vghtpe.gov.tw.
Abstract
BACKGROUND AND PURPOSE: Flat detector CT has been increasingly used as a follow-up examination after endovascular intervention. Metal artifact reduction has been successfully demonstrated in coil mass cases, but only in a small series. We attempted to objectively and subjectively evaluate the feasibility of metal artifact reduction with various metallic objects and coil lengths. MATERIALS AND METHODS: We retrospectively reprocessed the flat detector CT data of 28 patients (15 men, 13 women; mean age, 55.6 years) after they underwent endovascular treatment (20 coiling ± stent placement, 6 liquid embolizers) or shunt drainage (n = 2) between January 2009 and November 2011 by using a metal artifact reduction correction algorithm. We measured CT value ranges and noise by using region-of-interest methods, and 2 experienced neuroradiologists rated the degrees of improved imaging quality and artifact reduction by comparing uncorrected and corrected images. RESULTS: After we applied the metal artifact reduction algorithm, the CT value ranges and the noise were substantially reduced (1815.3 ± 793.7 versus 231.7 ± 95.9 and 319.9 ± 136.6 versus 45.9 ± 14.0; both P < .001) regardless of the types of metallic objects and various sizes of coil masses. The rater study achieved an overall improvement of imaging quality and artifact reduction (85.7% and 78.6% of cases by 2 raters, respectively), with the greatest improvement in the coiling group, moderate improvement in the liquid embolizers, and the smallest improvement in ventricular shunting (overall agreement, 0.857). CONCLUSIONS: The metal artifact reduction algorithm substantially reduced artifacts and improved the objective image quality in every studied case. It also allowed improved diagnostic confidence in most cases.
BACKGROUND AND PURPOSE: Flat detector CT has been increasingly used as a follow-up examination after endovascular intervention. Metal artifact reduction has been successfully demonstrated in coil mass cases, but only in a small series. We attempted to objectively and subjectively evaluate the feasibility of metal artifact reduction with various metallic objects and coil lengths. MATERIALS AND METHODS: We retrospectively reprocessed the flat detector CT data of 28 patients (15 men, 13 women; mean age, 55.6 years) after they underwent endovascular treatment (20 coiling ± stent placement, 6 liquid embolizers) or shunt drainage (n = 2) between January 2009 and November 2011 by using a metal artifact reduction correction algorithm. We measured CT value ranges and noise by using region-of-interest methods, and 2 experienced neuroradiologists rated the degrees of improved imaging quality and artifact reduction by comparing uncorrected and corrected images. RESULTS: After we applied the metal artifact reduction algorithm, the CT value ranges and the noise were substantially reduced (1815.3 ± 793.7 versus 231.7 ± 95.9 and 319.9 ± 136.6 versus 45.9 ± 14.0; both P < .001) regardless of the types of metallic objects and various sizes of coil masses. The rater study achieved an overall improvement of imaging quality and artifact reduction (85.7% and 78.6% of cases by 2 raters, respectively), with the greatest improvement in the coiling group, moderate improvement in the liquid embolizers, and the smallest improvement in ventricular shunting (overall agreement, 0.857). CONCLUSIONS: The metal artifact reduction algorithm substantially reduced artifacts and improved the objective image quality in every studied case. It also allowed improved diagnostic confidence in most cases.
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